More than 180,000 people have fled west Mosul as Iraqi forces battle to retake it from the Islamic State group, the Iraqi government said Monday.
Some 111,000 have sought shelter in 17 nearby camps and reception centres while many others have stayed with relatives, the ministry of displacement and migration said.
Iraqi forces backed by an international US-led coalition launched a drive to retake west Mosul on February 19 after seizing the city's eastern side the previous month.
They have since taken control of several districts including parts of the densely-populated Old City.
The Iraqi government says it can accommodate a further 100,000 displaced people in camps, but the United Nations says the numbers could rise way beyond that.
"Humanitarian agencies are bracing for the possibility that an additional 300,000-320,000 civilians may flee in coming weeks," the UN's aid coordination agency OCHA said.
The UN's humanitarian coordinator in Iraq, Lise Grande, said aid groups had spent months preparing for the Mosul operation.
"But the truth is that the crisis is pushing all of us to our limits," she said.
The aid operation for western Mosul is "far larger and far more complex" than in the east, she said.
"The main difference is that tens of thousands of families stayed in their homes in the east," she said. "In the west, tens of thousands are fleeing."
"If the number of people leaving the city increases faster than we can construct new plots, the situation could deteriorate very quickly," she added.
Iraq's second city, Mosul had an estimated population of two million before IS overran it in a lightning June 2014 assault.